This application is based on Japanese Patent Application No. 2000-270265, filed in Japan on Sep. 6, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
This invention relates to an in-tank fuel supply apparatus for installation in a fuel tank of a vehicle, for example. In particular, it relates to an in-tank fuel supply apparatus in which a fuel pump, a fuel filter, a pressure regulator, and a check valve are part of an assembly which can be installed in a fuel tank as a single unit.
2. Description of the Related Art
FIG. 12 is a cross-sectional elevation of a conventional in-tank fuel supply apparatus disclosed in Japanese Published Unexamined Patent Application Hei 11-241659 having a fuel pump, a fuel filter, a pressure regulator, and a check valve combined as part of an assembly for installation in a fuel tank. FIG. 13 is a schematic illustration of the apparatus of FIG. 12, and FIG. 14 is an enlarged cross-sectional elevation of a conventional pressure regulator which can be used as the pressure regulator of the apparatus of FIG. 12.
The fuel supply apparatus of FIGS. 12 and 13 is disposed in a fuel tank 1 and includes a fuel pump 2, an intake filter 3 disposed upstream of the inlet of the fuel pump 2, and a fuel filter unit 4 disposed downstream of the discharge port of the fuel pump 2. A filter element 6 is disposed inside a main housing 5 made from a molded resin. The fuel pump 2 is supported by a downwardly extending lower portion of the main housing 5. The discharge port of the fuel pump 2 communicates through a connecting pipe with a space within the main housing 5 at an inlet 5a on the upstream side of the filter element 6.
The fuel supply apparatus further includes an upper housing 7 made of a molded resin. After the filter element 6 is inserted into the main housing 5, the upper housing 7 is sealed to the main housing 5 in an oil tight manner by solvent bonding or other suitable method to enclose the filter element 6, so that fuel can flow within the fuel filter unit 4 from the inlet 5a through the filter element 6 to the outlet 5b. The upper end of the upper housing 7 has a flange formed thereon by which the fuel supply apparatus can be mounted on the upper surface of the fuel tank 1.
The fuel supply apparatus is equipped with a fuel supply passage 8 for carrying fuel from the outlet 5b of the fuel filter unit 4 to an unillustrated engine. The fuel supply passage 8 is integrally formed with the upper housing 7. A check valve 9 is provided in the fuel supply passage 8 for preventing reverse flow of fuel from the engine to the fuel filter unit 4. The fuel supply passage 8 and the outlet 5b are connected to each other by solvent bonding at the same time that the upper housing 7 is sealed in an oil tight manner by solvent bonding to the upper end of the main housing 5. A pressure regulator 10 is provided for maintaining the pressure of fuel supplied to the engine in a prescribed range. It returns excess fuel which is not supplied to the engine to inside the fuel tank 1. During normal operation of the fuel supply apparatus, the amount of fuel discharged by the fuel pump 2 is greater than the amount of fuel which is consumed by the engine.
FIG. 13 is a schematic illustration of the fuel supply apparatus of FIG. 12. This figure shows that the check valve 9 is disposed downstream of the filter element 6, and that the pressure regulator 10 is mounted on a pipe which branches off the nipple 8a of the fuel supply passage 8 downstream of the check valve 9.
In a fuel supply apparatus of this type, when the fuel pump 2 is operated, liquid fuel is sucked from the interior of the fuel tank 1 by the fuel pump 2 through the intake filter 3. The fuel is pressurized to 200-700 kPa by the fuel pump 2, and then it enters the fuel filter unit 4 through the inlet 5a. Coarse debris and other contaminants are removed from the fuel by the intake filter 3, while fine contaminants are removed from the fuel by the filter element 6 in the fuel filter unit 4. After passing through the filter element 6, the filtered fuel is discharged from the outlet 5b and passes through the fuel supply passage 8 through the check valve 9 to be supplied to the engine. The pressure of the fuel supplied to the engine is maintained in a prescribed range by the pressure regulator 10, which discharges excess fuel to inside the fuel tank 1 when the pressure in the fuel supply passage 8 exceeds a prescribed level due to an increase in the output of the fuel pump 2 or a decrease in fuel consumption by the engine. The check valve 9 maintains the fuel pressure in the engine when the fuel pump 2 is stopped.
In a fuel supply apparatus like that described above, since the pressure regulator 10 communicates with the fuel supply passage 8 downstream of the check valve 9, when the fuel pump 2 is stopped, in order to maintain the fuel pressure in the engine, the pressure regulator 10 must have a good ability to maintain a seal between its upstream and downstream sides.
An example of a pressure regulator having a good sealing ability is shown in FIG. 14, which is an enlarged cross-sectional elevation of a conventional pressure regulator disclosed in Japanese Published Unexamined Patent Application Hei 5-215048. In this pressure regulator 10, a movable valve 10c which is secured to a spherical bearing 10b is mounted on a diaphragm 10a for sensing fuel pressure. The valve 10c opposes a valve seat 10d which communicates with a discharge port.
When the fuel pressure increases to a level such that the force acting upwardly on the diaphragm 10a due to fuel pressure exceeds the downwards force exerted by a back pressure spring 10e, the diaphragm 10a deforms upwards and valve 10c separates from the valve seat 10d to create a gap. As a result, fuel is discharged through the gap between the valve 10c and the valve seat 10d, and the fuel pressure on the engine side of the pressure regulator 10 is maintained constant.
When the fuel pressure decreases below a certain level, the valve 10c is made to contact the valve seat 10d by the force of the back pressure spring 10e, and the discharge of fuel from the fuel regulator 10 is stopped. Since the movement due to deformation of the diaphragm 10a is not uniform, the valve 10c is supported by the spherical bearing 10b so as to be able to freely pivot so that the valve 10c can intimately contact the valve seat 10d and prevent leaks of fuel to the downstream side of the pressure regulator 10 to maintain the fuel pressure in the fuel supply passage 8.
While the pressure regulator 10 of FIG. 14 has good sealing performance, it has the drawback that it is expensive to manufacture due to the need to perform high precision finishing of the spherical bearing 10b, the valve 10c, and the valve seat 10d. Furthermore, the diameter of the diaphragm 10a must be fairly large in order to give the valve 10c good durability and in order to support the valve 10c in a manner such that it can freely pivot, and this leads to an increase in the outer dimensions of the pressure regulator 10, which is an impediment to obtaining a compact fuel supply apparatus.
The present invention provides a fuel supply apparatus which can employ an inexpensive pressure regulator having a simple and compact structure.
The present invention also provides a fuel supply apparatus which enables an engine which is supplied fuel by the fuel supply apparatus to be quickly restarted after being off for an extended period.
According to one form of the present invention, a fuel supply apparatus includes a fuel pump, a housing, and a filter element disposed in the housing and having an upstream side communicating with a discharge port of the fuel pump. A fuel supply passage communicates with the interior of the housing on a downstream side of the filter element for supplying fuel to an engine. A check valve for preventing reverse flow of fuel through the fuel supply passage communicates with a downstream side of the filter element, and a pressure regulator communicates with the upstream side of the filter element.
The apparatus may further include a sedimentation flow path communicating with an outlet of the pressure regulator for removing sediment from fuel discharged from the pressure regulator and returning the fuel to inside the fuel tank.
The sedimentation flow path may include a recess for receiving sediment which settles from fuel passing through the sedimentation flow path.
The apparatus may further include a pump holder which is attached to the housing and supports the fuel pump, and a vibration absorber disposed between the pump holder and the fuel pump, wherein the sedimentation flow path comprises a space formed between an outer periphery of the fuel pump, an inner periphery of the pump holder, and the vibration absorber.
The housing may include a passage communicating between an upper portion of the housing and the pressure regulator to prevent the housing from running dry when an engine to which the fuel supply apparatus supplies fuel is turned off for an extended period.
The apparatus may further include a pump holder surrounding the fuel pump for supporting the fuel pump from the housing, the sedimentation flow path comprising a space formed between an outer periphery of the fuel pump and an inner periphery of the pump holder.
A portion of the space defined between the inner periphery of the pump holder and the outer periphery of the fuel pump may be vertically partitioned to define an annular sedimentation flow path extending along the outer periphery of the pump holder, and the sedimentation flow path may include substantially cylindrical vortex spaces defined between a plurality of fins projected from the inner periphery of the pump holder and having blind holes disposed at the bottom of the vortex spaces for trapping the sediments.